Keycaps are a fairly niche market, so I have no idea where to look in order to find quality sets -- especially specific colors or layouts. It seems that the market is so small that you can only find what you are looking for if you get lucky because there is no one place that keeps a large stock of everything.
Right now I am looking for thick (which I have come to understand as ≥1.5mm) PBT keycaps in a beige color, in standard measurements (CM QFR), without any printing on them.